Arsenic in drinking water - Problems and solutions

The current United States maximum contaminant level for arsenic in drinking water is set at 50 mu g/l. Because of the cancer risks involved, Canada ha s already lowered the maximum contaminant level to 25 mu g/l; the United St ates Environmental Protection Agency is reviewing the current allowable lev el for arsenic with a view of lowering it significantly. Various treatment methods have been adopted to remove arsenic from drinking water. These meth ods include 1) adsorption-coprecipitation using iron and aluminum salts, 2) adsorption on activated alumina, activated carbon, and activated bauxite, 3) reverse osmosis, 4) ion exchange and 5) oxidation followed by filtration . Because of the promise of oxidation-filtration systems, column studies we re conducted at the University of Regina to examine oxidation with KMnO4 fo llowed by filtration using manganese greensand and iron-oxide coated sand t o examine the removal of arsenic from drinking water; these results were co mpared with the data from ion exchange studies. These studies demonstrated that As (III) could be reduced from 200 mu g/l to below 25 mu g/l by the ma nganese greensand system. In the case of manganese greensand filtration, ad dition of iron in the ratio of 20:1 was found necessary to achieve this rem oval. (C) 1999 Published by Elsevier Science Ltd on behalf of the IAWQ. All rights reserved.